Method for Preventing a Vehicle from Rolling Away, and Computer Program Product

ABSTRACT

The invention relates to a method for preventing a vehicle, in particular a commercial vehicle, from rolling away, wherein the vehicle is equipped with a compressed air treatment unit (APU) and at least one associated pressure sensor for detecting at least one pressure in a brake circuit, in particular with an electronic compressed air treatment unit (E-APU), and a self-braking system (for example ASR, ESP, FDR, EBS). The invention further relates to a computer program product, which carries out such a method. Furthermore, the invention relates to an electronic compressed air treatment unit (E-APU) and to a self-braking system (ASR, ESP, FDR, EBS).

The present invention generally relates to a method for preventing a vehicle, in particular a utility vehicle, from rolling away, wherein the vehicle is equipped with a compressed-air processing system (APU) and at least one associated pressure sensor for detecting at least one pressure in a brake circuit, in particular with an electronic compressed-air processing system (E-APU), and with a self-braking system (for example ASR, ESP, FDR, EBS). Also, the invention relates to a computer program product for executing such a method. The invention further relates to an electronic compressed-air processing system (E-APU) and to a self-braking system (ASR, ESP, FDR, EBS).

Particularly in Scandinavian countries, it is a legal requirement for the parking brake of a vehicle to only be able to be released when filling compressed air if the vehicle driver performs this action manually, that is by operating a lever, valve or switch for example. This is intended to prevent the vehicle from rolling away without the vehicle driver. Although preventing the vehicle from rolling away is not necessarily a legal requirement, vehicle drivers, in particular in Scandinavia, have become accustomed to this safety function, and therefore vehicle manufacturers continue to provide this functionality.

A dangerous situation of this kind can occur, for example, in the case of a utility vehicle that is braked using compressed air, if the vehicle has been parked on an incline and the compressed-air storage means have been depressurized overnight. Although the vehicle is held in its existing position by the parking brake, which is designed as a spring-loaded brake, by virtue of spring force, as soon as the vehicle driver starts the engine of the vehicle, the compressed-air storage means are filled in a defined order. In the process, the compressed-air storage means of the service brake circuits are usually first filled with compressed air in order to ensure that the vehicle can be braked at any time. The spring-loaded brake would only then be supplied with compressed air, resulting in the release of the spring-loaded brake. Therefore, if the vehicle driver were to start the engine and wished to release the parking brake by means of an operating device in the cab of the vehicle, the vehicle would not begin to move since the compressed-air storage means of the service brake circuit first have to be filled. If the vehicle driver then leaves the cab in order, for example, to find the fault preventing the vehicle from moving away or, for example, to clean the windshield, the compressor that supplies compressed air to the compressed-air storage means would continue to deliver compressed air during this time. As soon as the compressed-air storage means of the service brake circuits are filled, the parking brake would then also be supplied with compressed air, and this would lead to release of the parking brake, as a result of which the vehicle could begin to move. There is a danger here of the vehicle driver and/or other people being run over by the driverless vehicle.

In order to prevent this, various mechanical solutions employing further pneumatic valves have been provided to date. One disadvantage of a mechanical solution of this kind is that different systems have to be provided for different countries, as a result of which higher costs are incurred.

It is therefore an object of the present invention to provide a cost-effective method for preventing a vehicle from rolling away, and also a computer program product, as well as an electronic compressed-air processing system (E-APU) and also a self-braking system (EBS, ASR, FDR, ESP).

This object is achieved by patent claims 1, 12, 13 and 14.

In an advantageous embodiment of the invention, the pressures are read into the electronic braking system (EBS) from the parking brake circuit by means of independent sensors or by means of electrically modulated signals or preferably by means of a data bus (for example a CAN bus standardized in accordance with SAE J 1939, Air Supply Pressure message, from the E-APU).

In a further embodiment of the present invention, the method is implemented in the E-APU by the pressures being read into the E-APU from the parking brake circuit by means of sensors and being evaluated by the electronics of the E-APU. If the service brake is intended to be applied, the E-APU sends a signal to the electronic braking system (EBS).

In another embodiment, the method is realized in an independent controller that communicates with the electronic compressed-air processing system (E-APU) and the self-braking system (FDR, ASR, ESP, EBS).

In a further embodiment, the electronic compressed-air processing system (E-APU) and the self-braking system (FDR, ASR, ESP, EBS) are combined to form one device, and a method according to the inventive embodiments is implemented in this device.

In the following text, an electronic compressed-air processing system (E-APU) is always assumed to be used, wherein all that is required for the inventive methods described here is that information, that is pressure values, at least of one service brake circuit are present, it being possible to draw conclusions about the pressure in the parking brake circuit from this information. Therefore, the inventive methods described here can also be applied to vehicles that can determine at least one pressure value of a service brake circuit and that additionally have a self-braking system (FDR, ASR, ESP, EBS).

The term “self braking system” (FDR, ASR, ESP, EBS) is intended to mean brake systems that allow the vehicle to be braked automatically, that is without the involvement of the vehicle driver. For example, known vehicle dynamics control systems (FDR) or electronic stability programs (ESP) or else transmission slip control systems (ASR) are self-braking systems in line with this definition. So-called electronic braking systems (EBS) are also a self-braking system of this kind, provided that the vehicle can be automatically braked.

The term “release threshold” is intended to mean the pressure that has to be present at least in the parking brake, which is in the form of a spring-loaded brake cylinder, so that the parking brake can be reliably released. This ensures that the vehicle driver, if he wishes to release the parking brake, can release the parking brake and can immediately drive away with the vehicle. Therefore, the situation cannot occur of the parking brake not being able to be released on account of an excessively low pressure in the parking brake circuit that could possibly cause the vehicle driver to leave the vehicle. By way of example, a pressure value of approximately 4 bar can be used as a release threshold. It goes without saying that this release threshold can be set at different levels depending on the vehicle parameters, for example vehicle weight, trailer operation, etc. Therefore, the release threshold can be in the range of from approximately 1 bar to approximately 6 bar depending on vehicle parameters. The release threshold is preferably approximately 4 bar.

The functions disclosed up to this point and the solution according to exemplary embodiments of the present invention will be described below with reference to the appended drawing figures, in which

FIG. 1 shows a first known solution by means of a pneumatic valve,

FIG. 2 shows a second known solution by means of a solenoid valve, and

FIG. 3 is a flowchart of a solution according to an embodiment of the present invention.

FIG. 1 shows a first known solution having a pneumatic valve, which is illustrated as a 3/2-way valve in the figure, in the parking brake circuit, wherein the pneumatic valve closes if the pressure in the parking brake circuit, that is the compressed-air storage means from which the parking brake is supplied with compressed air, falls below a specific pressure threshold. Therefore, in order to be able to release the parking brake, first the parking brake (illustrated as a handbrake valve here) and also the pneumatic valve have to be manually operated.

FIG. 2 shows a second known solution having a solenoid valve, wherein the solenoid valve, in the operated state, prevents the circuit 23 or 23.1 (parking brake circuit) from being filled. In this case, an electronic control switches the solenoid valve if the pressure in the parking brake drops.

FIG. 3 is a flowchart of a solution according to an exemplary embodiment of the present invention. In this case, a check is made in a first step to determine whether the vehicle is stationary (“yes”) or moving (“no”). This information can be determined, for example, by means of checking a speed signal (speedometer signal, wheel rotation speed information). If the vehicle is stationary, a check is made, in a second step, to determine whether the pressure in the parking brake circuit is lower than a release threshold for the parking brake. In this case, the term “release threshold” is intended to mean the pressure that has to be present at least in the parking brake, which is in the form of a spring-loaded brake cylinder, so that the parking brake can be reliably released. By way of example, a pressure value of approximately 4 bar can be used as a release threshold. If this is the case (“yes”), the service brake is then applied. A check is subsequently made, in a third step, to determine whether the vehicle driver actuates an indicator (for example in the form of a switch, pushbutton, seat-occupation switch or a pedal) in order to indicate that the driver is present in the vehicle cab. The vehicle can be moved, that is the service brake is released, only if this operation of the indicator has been carried out and additionally there is enough pressure in the parking brake circuit to release the parking brake. The vehicle cannot be moved, and as a result the vehicle is also prevented from rolling away, provided that the driver has not operated the indicator or additionally there is not enough pressure in the parking brake circuit.

It is not absolutely necessary to check whether the vehicle is stationary; it would also be feasible to only detect whether the pressure in the parking brake circuit is lower than a release threshold for the parking brake.

In this case, the pressure in the parking brake circuit can be determined or at least estimated from pressure signals, for example from pressure sensors in the respective circuits. It is also possible to at least estimate the pressure in the parking brake circuit from the service brake circuits 21 and 22 and to use the pressure correspondingly.

In a further embodiment of the invention, it is also possible for the service brake to be released as early as after operation of the indicator by the vehicle driver since, at this time, the driver is in the cab, and a check is only then made to determine whether there is enough pressure in the parking brake circuit to release the parking brake. If there is not enough pressure in the parking brake circuit, the service brake can be operated again in order to prevent the vehicle from rolling away if the vehicle driver has left the vehicle in the meantime.

In another embodiment of the invention, provision is also made for the service brake to be applied only if it is detected that the vehicle has started to roll.

The described method embodiments therefore provide a standstill safety function by making demands of the service brake. This provides a more cost-effective implementation functionality in comparison to conventional solutions since the solution according to the inventive embodiments can be realized purely by software in a self-braking system.

By way of example, an electronic braking system (EBS) can, after the system is started, monitor the pressures in the parking brake circuit that are sent by the electronic compressed-air processing system (E-APU) (or another device). If a pressureless/low-pressure system in line with the criteria of the standstill safety function described here is detected, the service brake is independently braked (for example by opening the inlet valve into the axle modulators) by means that are available to the electronic braking system (EBS).

By way of example, the electronic compressed-air processing system (E-APU) evaluates the pressures and, if the condition for standstill safety functioning is detected, sends a message to the self-braking system (EBS, ASR, FDR, ESP) so that the service brake is applied. The self-braking system (EBS, ASR, FDR, ESP) evaluates this message and brakes the vehicle with the service brake for as long as the message is sent.

Instead of a message, an analog signal line can also be used between the electronic compressed-air processing system (E-APU) and the self-braking system (EBS, ASR, FDR, ESP).

By way of example, a so-called XBR (eXternal Brake Request) can be used as a standardized CAN SAE J1939 message.

Therefore, if a pressureless system is detected, that is no pressure is detected in the compressed-air containers of the service brake circuits of the vehicle, when the vehicle is at a standstill (for example, after the electronic compressed-air processing means (E-APU) is switched on, the pressure in the parking brake circuit is lower than 4 bar), the self-braking system in the vehicle then brakes the vehicle independently, that is without the vehicle driver, using the service brake, in order to prevent the vehicle from rolling away when the system is being filled. The service brake is released only if the driver's presence in the cab is indicated (indicator), for example by operating the brake or clutch pedal or by depressing the accelerator, and the parking brake circuit has enough pressure.

In this case, the service brake has to be supplied with air (that is filled) until there is enough pressure in the system for the service brake to reliably hold the vehicle. Under certain circumstances, this is the case only after a certain time if the compressor has built up enough pressure in the service brake circuits. Since at least one service brake circuit is filled before the parking brake circuit in accordance with the prior art, reliable braking of the vehicle is ensured by means of the service brake circuit before the parking brake opens.

Communication between the respective controllers, for example between the controller of the electronic compressed-air processing system (E-APU) and the controller of the self-braking system (ASR, FDR, EBS, ESP), can be ensured by no message/signal being sent to the self-braking system (ASR, FDR, EBS, ESP) in the event of a loss of electrical power to the electronic compressed-air processing system (E-APU), as a result of which the self-braking system (ASR, FDR, EBS, ESP) also operates the service brakes, as a result of which the vehicle is prevented from moving or rolling away.

If the electrical power is lost (can be detected since there are no corresponding CAN messages) in the case of a self-braking system (ASR, FDR, EBS, ESP), the electronic compressed-air processing system (E-APU) can discharge pressure (for example by means of the “purge valve”) or switch off the compressor in order to prevent the vehicle from building up pressure in the parking brake, as a result of which the parking brake would be released. This again prevents the vehicle from rolling away or moving away.

Advantageously, a cost saving is achieved by the described safety function being realized by adapting the software in an existing electronic compressed-air processing system (E-APU) in conjunction with a self-braking system (ASR, FDR, EBS, ESP). Furthermore, no additional mechanical components are required. A solution that is carried out by means of software further provides the advantage that it can be implemented rapidly in existing mass-produced products. Furthermore, it has the advantage that an improvement in respect of quality is achieved by virtue of a reduction in complexity, that is fewer components, which could potentially fail.

In a further embodiment of the present invention, provision is made for the service brake to be automatically operated each time the vehicle is started (“Ignition on”), independently of the existing pressure in the system.

In a another embodiment, the service brake is operated only after the vehicle is started (“Ignition on”), and not after each time the vehicle is stopped, as a result of which the switching conditions for the operation of the service brake according to the standstill safety function presented here are not rechecked every time.

It should be understood that the described embodiments can be combined with one another, provided that they do not contradict one another. 

1. A method for preventing a vehicle from rolling away, wherein the vehicle is equipped with at least one pressure sensor in at least one brake circuit and with self-braking system (ASR, ESP, FDR, EBS) and also with a parking brake, characterized by the following steps: determining whether the pressure in the compressed-air circuit from which the parking brake is fed is below a release threshold, operating the service brake if the pressure in the compressed-air circuit from which the parking brake is fed is below the release threshold.
 2. The method as claimed in claim 1, characterized in that, it is determined in a further step whether the vehicle is stationary.
 3. The method as claimed in claim 1 or 2, characterized in that the service brake is operated only if it is detected that the vehicle begins to roll.
 4. The method as claimed in at least one of the preceding claims, characterized in that it is determined in a further step whether the vehicle driver has operated an indication means.
 5. The method as claimed in at least one of the preceding claims, characterized in that the service brake is released if the vehicle driver has operated an indication means.
 6. The method as claimed in claim 5, characterized in that the service brake is released only if the pressure in the compressed-air circuit from which the parking brake is fed is additionally sufficient to release the parking brake.
 7. The method as claimed in either of claims 2 and 3, characterized in that a speed signal, a speedometer signal or a wheel rotation speed sensor signal is used to determine whether the vehicle is stationary or rolling.
 8. The method as claimed in claim 1, characterized in that a pressure value in the range of approximately 1 bar to approximately 6 bar is used as the release threshold.
 9. The method as claimed in claim 1, characterized in that a pressure value of 4 bar is used as the release threshold.
 10. The method as claimed in claim 4, characterized in that a signal from a switch or pushbutton or a seat-occupation device or a pedal is used as the indication means.
 11. The method as claimed in one of the preceding claims, characterized in that the service brake is operated only after the vehicle is started (“Ignition on”).
 12. A computer program product, characterized in that it executes a method as claimed in at least one of claims 1 to
 11. 13. An electronic compressed-air processing system (E-APU), characterized in that a method as claimed in at least one of claims 1 to 11 is implemented in a controller of the electronic compressed-air processing system (E-APU).
 14. A self-braking system (ASR, ESP, FDR, EBS), characterized in that a method as claimed in at least one of claims 1 to 11 is implemented in a controller of the self-braking system (ASR, ESP, FDR, EBS). 